A compiled module is a script containing a library of user-defined functions that we want to call frequently from other tests. When we load a compiled module, its functions are automatically compiled and remain in memory. We can call them directly from within any test.

Compiled modules can improve the organization and performance of our tests. Since we debug compiled modules before using them, our tests will require less errorchecking. In addition, calling a function that is already compiled is significantly faster than interpreting a function in a test script.